Field
The present disclosure relates to a negative electrode active material layer composition for a rechargeable lithium battery, a method of preparing the same, and a rechargeable lithium battery including the same.
Description of the Related Technology
A rechargeable lithium battery has recently drawn attention as a power source for small portable electronic devices. The battery uses an organic electrolyte solution and has a discharge voltage twice or more higher than that of a conventional battery which uses an alkali aqueous solution. Thus, the lithium battery has a high energy density.
As for positive active materials of a rechargeable lithium battery, the lithium-transition metal oxide having a structure capable of intercalating lithium ions, such as LiCoO2, LiMn2O4, LiNi1-xCoxO2 (0<x<1), and the like may be used.
The negative active material of a rechargeable lithium battery can include a Si-based negative active material and various carbon-based negative active material such as artificial graphite, natural graphite, and hard carbon. These negative active materials may all intercalate and deintercalate lithium ions.
Since the Si-based negative active material is more irreversible than the carbon-based negative active material, a rechargeable lithium battery including the Si-based negative active material shows lower initial efficiency than a rechargeable lithium battery including the carbon-based negative active material.
In addition, the Si-based negative active material repeatedly expands and contracts during charge and discharge. The occurring swelling phenomenon destroys a SEI (solid electrolyte interphase) film on the surface of the negative electrode. In order to prevent the damage caused by the volume change of the negative active material, a new SEI passivation film is formed, and thus, the SEI layer becomes thick on the surface of the negative electrode. Accordingly, the battery cycle-life characteristics are deteriorated, a space due to volume expansion is limited. The electrolyte may leak due to mechanical stress and further deteriorate the performance of the battery.
Accordingly, development of a Si-based negative active material capable of increasing initial efficiency and increasing cycle-life is required.